Transformer and coil system



Oct. 22, 1929. 1.. JONES TRANSFORMER AND OQIL SYSTEM Original Filed June 1927 lNV-ENTOR tesier L. Jon es ATTORNEYS Patented Oct. 22, 1929 PATENT OFFICE.

LESTER L. JONES, OF ORADELL, NEW JERSEY TRANSFORMER AND COIL SYSTEM Application filed June 1 1927, Serial No. 195,631. Renewed September 10, 1929.

This invention relates to transformer and coil systems, and has special reference to the provision of improved transformers and coil systems adapted for use with electron dis- 5 charge devices r relays such as are employed in radio circuits or systems.

A prime object of my present "invention centers about the provision of a transformer specially adapted for use with three element electron discharge devices or relays, especially for the securing ofamplification of alternating currents having a wide range of frequency without-adjustment, such transformers being of the socalled untuned or is broad band type.

It has been found that such transformers of the untuned type do not have a constant amplification over the whole frequency band for which they are intended. This undesirable characteristic is noticeable in audio frequency transformers and is especially objectionable in radio frequency transformers. In transformers for the amplification of the frequency band of 500,000 to 2,000,000 cycles per second the variation in amplification is most ings which I designate or call a short wave oscillation. All prior types of transformers are subject to this mode of short wave oscillation in a frequency band closely adjacent to the frequency band for which the transformer is designed. In the prior art, at-

tempts have been made to utilize this second mode of oscillation by modifying the design so as to include it in the frequency band for which the transformer is designed.

I have found that this short wave mode of oscillation is primarily due to the leakage of magnetic flux between the primary and secondary windings. In transformers which are wound in opposite directions the short wave mode of oscillation may be predetermined from the leakage inductance of the trans former and the distributed capacities of the coils. In a general.,way, in this type of transformer, the frequency of the short wave oscillation is determined by a capacity which is mainly the sum of the distributed capacities -ofthe primary and secondary windings and an inductance which is approximately the parallel inductance of the primary and secondary. windings, which parallel inductance may be defined as In transformers wound in the same direction. the short wave oscillation is again de termined by a capacity, which, however in this case, is mainly the capacity between the primary and secondary windings and an inductance which is approximately the series inductance of the primary and secondary windings which maybe defined as L +L,-2M

In these formulas L self-inductance of primary L =self-inductance of secondary M mutual inductance between primaryand secondary Y I have discovered that it is feasible to completely suppress this objectionable short able short Wave mode of oscillation, that great care must be taken in winding the primary and secondary filaments of the transformer so as to produce a substantially unity coupling between the primary and secondary transformer windings; and by this I mean that the primary and secondary windings should nowhere be separated by a space greater than the space occupied by the insulation coverings of the wires or filaments.

It a prime desideratum, therefore, of my present invention to pno vi=de=n transformer having a bifilar construction so designed as to effect the elimination of the leakage inductance between the windings, all to the end of obviating or completely suppressing the short Wave mode of -oscillation. I

A further primeobject of my present inyention centers about the .provision of a transformer, prefenably of the bifilar type, which is astatic. .As .is well known, .it is a desideratum of certain types of selective and sensitive radio jreceiving apparatus and in apparatus emp'loyable near transmitting stations, to construct the coils or windings of thereeeiving apparatus so thatjhey are ,nncoupled magnetically to other coils and apparatus in the receiving circuit or to the transmitting apparatus. To accomplish the magnetic uneouplinglof the coils to other apparatus, various types of coil windings have hitherto been designed, such as double D w indings, toroid windingsand binocular coils; These prior types of coil windings have, however, been found insuflicient to produce the desired results on-account of their relatively large 'external fields near the coil whichproduce considerable coupling to other parts, and even between similar coils when placed at a moderate distance apart. To re duce the inter-magnetic couplings between similar coils in the radio receiving set with the use of'such ,prior structures, it has been found necessary. to so relatively arrange the coils one with respect to the other in the radio receiving set as to minimize the reacting fields. Other structural difficulties, such as the large volume of winding required and the difiiculty of winding methods have also hinder'ed'the use of these prior and known types of winding coils.

It is therefore a prime desideratum of my present invention to provide a transformer or an inductance coil system designed and constructed so that the external magnetic 'field is reduced to such a minimum that the 'coilis substantially de-coupled magnetically from surrounding apparatus and may be placed in close proximity to other similar coils of a radio receiving system without ter-magnetically reacting with the same.

To the accomplishment of the foregoing: and such other objects as will hereinafter appear, my invention consists in the elements and their relation one to the other, as her inafter more particularly described and sought to he defined in the claims; reference being had to the accompanying lrawings which show the preferred en'ibediincz'it of my invention, and in which Fig. 1 is a perspective view showing a pre ferred form of construction of the bililar astatic transformer of my invention,

Fig. 2 is an enlarged front elevational view thereof depicting the manner of winding the sections of the transformer and portraying thebifilar character of the construction,

Fig. 3 is a cross-sectional view thereof drawn to an enlarged scale showing the preferred mathematical relation between the dimensions "thereof to secure astaticism,

Fig. 4 is a view showing a preferred manner of producing close juxtaposition of the filaments of the transformer,

Fig. 5 is a cross-sectional view of. .a modified form of the transformer showing either a step-down or step-up ratio of trans formation,

Fig. 6 is a wiring diagrammatic view of F ig. 5,

Figs. '7 and 8 are two other modifications of step-up or step-down transformations enibodying the invention, and

Fig. 9 is a side face view of the structure shown in Fig. 8 drawn to a reduced scale.

To accomplish the result of suppressing the objectionable short wave mode o'f-osc-illa- 'tion, the transformer of my invention oomprises primary and secondary windings and S wound bifilarly, that i-s to say, wound so that the filaments of the windings are arranged in close juxtaposition substantially throughout their entire lengths, as clearly shown in Figs 1,2 and 4 of the-drawings, and

as diagrammatically illustrated in part of- Fig.6 of the drawings. The i uxt-aposition or contiguous arrangement of the primary and secondary filaments P and S 18 such as to produce substantial unity coupling between the windings, that is to say, the primary an: secondary filaments are separated by a space no greater than the space occupied by the insulating covering of the wires or filaments. This is depicted in Fig. 4 of the where i and z" designate the insulating coverings of the primary and secondary filaments P and .8 respectively. To a sist in producing this close juxtaposition-over substantially the whole length of the filaments, the filaments P and S are twisted during the w'nding operation with a relatively large pitch, that is to say, with a pitch which is relatively large compared tothe diameters of the filaments. This is shown particularly in Figs. 2 and i of the drawings where the windin' s are shown transposed by twists in regions designated as t, t. This frequent transposition of the windings materially aids in holding the wires or filaments close together throughout their entirelength, this so as to producethe intended results. While I prefer,-for ease and-economy of operation, to effect the close juxtaposition by twisting,- it will be apparent that the same result may be accomplished in other ways, as for example, by securing the filaments to gether at points along their lengths- 4i I have found that a transformer constructed and wound in this manner exhibits extremely desirable characteristics. By exercising care to prevent a separation between the filaments greater than the separation produced by the insulation, I am enabled to eliminate the undesired leakage inductance between the windings substantially completely. I have found the transformer suitable for automatictuning and when so used I have found the same to give higher average amplification with a more constant value over the wave length-band than any other type of-transformer thus far developed. The transformer of my invention may be used without automatic tuning in any way whatsoever without developing disturbing interstage oscillations which-have been the bugbe ar ofprior' types of transformers and which give-wise to the necessity of iron cores to overdamp the transformers and stop oscillation, or the'use-of grid biasing potentiometers to reduce the tube amplification and increase the secondary losses of the transformer-by reason of passage of excessive grid current. Theeiiiciency of this transformer construction is in some measure due to the'high capacity between the windings'whichaccompanies the close spacing of the primary and secondary filaments through out their entire lengths. "The twisting of the filament pair in effectively preventing any primary turn from developing appreciable capacity at a different potential with respect to a secondary turn also contributes to the efliciency of the transformer. Anotherefi'ect which is contributory to the successful result produced is the obtaining of relatively large air spaces in the winding due to the fact that the twisted pair may be woundat random; and these air spaces tend to reduce the distributed capacity of the coil which should be a minimum for the purpose of untuned amplification. 1

. To produce the ma neticallyastatic results hereinbefore described, the transformer of my invention is made to comprise two coil sections A and B shown particularly in Figs. 1 to 3 of the.drawings,'each coil section being composed of a plurality of windings, the windings of the sections A and B being wound in opposite directions, as clearly shown by the arrows in F ig. 2 of the drawings. To produce these coil sections I provide a spool 10 forming the transformer core. This spool may be made of wood or other insulation material, said spool being provided with grooves 11 and 12 In which the COIlSGCtlOIlS are wound.

To produce a magnetic fieldat a distance which is substantially'equal to zero, I have found that the coil sections A and B should desirably be arranged co-axially with the windings of the coil section A equal in number to the windings of the coil section B. Optimum results'are obtained when the coil sections A andB are separated b a distance equal to the average diameter 0 a coil sectionyand this is depicted in F ig. 3 of the drawings where the separation between the coil sections A and B, that is to say, the separation between their centers-is represented by D and where the average diameter of the coil section is one-half-the sum of the mini mum diameter d and the-.maximum diameter (1 The distance D is thus preferably -made-equal*to one-half the sum of'the diameters d and'd. :I have found-that-where the coil sections are farther apart than the distance D, the coil system loses astaticism very rapidly, and -on.the other. hand, where the coil sections are closer together than the distance D, thei'useful inductance decreases rapidly on' account of the growth of the bucking or reverse mutual. i V

It will be'ap parentthat the astatic characteristic of the transformer may be used without the leakage eliminating characteristic and vicewersa,'it being understood that the preferred transformer construction shown in Figs-:1 to4'iembodies both-characteristics in the preferred'manner. Itrwill be also appreciated thatthe astatic characteristic is generic to inductance coil systems whether or not sucli systems' are made-in theform of a transformeia; 1. :3 L "In Figs.;1 t0'J3-Of the drawings, the transformeris niade witha .one-to one .ratio of transformation. The .-bifilar transformer of m present invention, however, may be made with either step-up or step-down ratios of transformation, and this is depicted in Figs. 5 to .9 of the drawings. i

. In the modification shown in Figs. 5 and 6 of the drawings, the transformer is shown to comprise primary and secondary windings P and S having portions wound bifilarly with the filaments arranged in close juxtaposition and forming one transformer section with one of said windings having a portion forming a single wire wound .section. Thus the primary and secondary windings P, S are wound bifilarly in a section designated bifilar, the secondary winding having a portiondesignated single wire winding which represents the single wire wound section. As shown in Fig. 5, the single wire wound section is preferably first wound on the core 10 on which the bifilar section is wound. The terminals of the primary and secondary windings are connected to audion circuits as indicated by the reference characters at such terminals shown-in-Fh'gs. 5 and 6 of the drawings, the

reference characters being F for filament,

Pd for .plate, G for grid, and B-v'r for the positi eside of-the B battery.

V-Viith a construction such as shown in Figs. 5 and 6 it :becomes possible :to use .a ft-ransformer of other than a one itoone ratio having a very high mutual inductance or a very low leakage and yet secure small die-leotnic :and

capacity losses. ln amplifying at vei-ydiig -h frequencies, one of the chief difficulties lies in the elimination of capacity acrossit'hesecondary winding. The amangement -shown in these Figs. 5 and 6 permits of a step-up transformer having minimum 'd-istrib'uted capacity and [maximum mutual. inductance without the-use of iron cores. 1

.In Fig. f the'drawings I show an alternative form of construction in which the bifilar coil wound in a groove .13 of the spool or core lO ,:and the single wire winding is "wound fill a groove 14 in said spool. The terminals of the composite windings are designated in Fig. 7 with the same reference characters as thosc in Fig. 5.

Another alternative construction of this composite winding is shown in :Figs. Sand 9 of the drawings wherein the biliilar coil 'is wound superposed over the single coil in a V-shaped channel 15 provided inthe core or spool 10. Preferably this spool is provided with orifices 16, .16 produced bydril-ling out the insulation for the purpose 101E further minimizing the 1 capacity.- Tlh'ewterminals of the windings in 8 :are designated "by nefenence characters similar :to those of :Figs. 5t0 7. 1 i i The use and operation, the method ofwinding and the advantages of the transfonme'r and coil system of my present invention will in the main be apparent from the above detailed description thereof While I have shown and described my invention .in the HHB- ferred form it will also be .apparent that many changes and modifications may be made in the structure disclosed without departing from the spirit of the invention, defined in the following claims.

I claim:

1. An :astzi'tic bifilar transformer comprising primary-and secondary windings wound bifilarly, similar parts of the filaments of said windings being arranged close juxtaposition throughout their-lengths, said windings comprising two axially spaced sect ions substantially equal in size and oppositely wound.

2. An astatic bifilar transformer comprising primary and secondary windings wound bifilarly, similar parts of the filaments of-said windings being arranged in close juxtaposition throughout their lengths, said windings comprising two co-axially arranged sedions equal in size and oppositely wound.

3. An astatic bifilar transformer comprising primary and secondary windings wound 'bifilarly, similar parts of the filaments of said windings being arranged close means? position throughout their lengths, said Windings comprising-"two sections substantially equal in size and oppositely wound, said sections being iarranged co-axially with the separation between their centers substantially equal to the average diameter of a coil section.

4. An asta'tic bifilar transformer comprisin primary and secondary windings wound bi arly, similar partsvof the filaments of said windings being arranged in close j-uxta position throughout their lengths with a substantial unity coupling, said windings comprising two sections equal in size and oppositely wound, said sections being separated a distance substantially equal to the average diameter of-a coil section.

5. An astatic transformer comprising primary and secondary windings wound in the same form, said windings together comprising-two axially spaced sections substantially equal in size and oppositely wound.

6. An astatic transformer comprising -pri-. mary and secondary windings wound together in the same form, said windings together comprising twocdaxially arranged sections, the said sections having windings equal in number and oppositely wound.

7. An ast-atic transformer comprising primary and secondary windings coupled together with a substantially unity'coupling, said windings comprising two coil sections substantially equal in size and oppositely wound, said sections being arranged co-axially with the separation between their centers substantially equal to the average diameter of a coil section. '8. An astatic transformer comprising primary and secondarywindingsdivided into two coil sections, said sections having windings substantially equal in number and oppositely wound and said sections being arranged co-axially with the separation between their centers substantially equal to the average diameter of a coil section.

9. An astatic coil comprising two coil sections arranged co-axially, the said coil sec. tions having windings equal in number and oppositely wound, the separation between the centers of said windings being substantially equal to the average diameter ofa coil sec tion, thesaid coil sections having windings in size, number and arrangement to produce a high resulting inductance with a small distributed capacity.

10. An astatic bifilar transformer comprising primary and secondary windings wound bifilarly, similar parts of the filaments of said windings being arranged in close juxtaposition throughout their lengths, said Windings comprising a plurality of axially spaced coil sections connected in circuit, said coil sections being wound in opposite directions to produce oppositely directed fluxes and being spaced a distance apart to produce a resulting self-inductant'e of substantial magnitude, the spacing between and the product of the number of turns and area of each of said oppositely wound coil sections being such as to produce substantially neutralizing magnetic fields at a distance.

11. An astatic bifilar transformer comprising primary and secondary windings wound bifilarly, similar parts of the filaments of said windings being arranged in close juxtaposition throughout their lengths, each of said windings comprising a plurality of coil sections connected in circuit, said coil sections being wound and connected to produce oppositel Y directed fluxes of substantially equal magnitude and being spaced axially a distance apart to produce a resulting self-inductance of the coil of substantial magnitude and to produce substantially neutral izing magnetic fields at a distance.

12. An astatic bifilar transformer comprising primary and secondary windings wound bifilarly, similar parts of the filaments of said windings being arranged in close juxtaposition tl'iroughout their lengths,

said windings comprising a plurality of coil sections wound on the same coil and connected in circuit, said coil sections being wound in opposite directions to produce oppositely directed fluxes and being spaced a distance apart to produce a resulting selfinductance of substantial magnitude, the product of the number of turns and area of one coil section being substantially equal to the product of the number of turns and area of the other coil section, and the distance between said coil sections being substantially small, whereby neutralizing magnetic fields are produced at a distance.

13. An astatic transformer comprising two windings, similar parts of the filaments of said windings being wound with a substantially unity coupling therebetween, said windings comprising a plurality of coil sections wound in opposite directions to produce oppositely directed fluxes and being spaced apart a distance to produce a resulting self-inductance of substantial magnitude, the said coil sections being spaced apart and the product of the number of turns and area of one coil section being related to the product of the number of turns and area of the other coil section so as to produce neutralizing magnetic fields at a distance.

14. An astatic transformer comprising two windings, similar parts of the filaments of said windings being wound with a substantially unity coupling therebetween, said windings comprising a plurality of coil sections wound in opposite directions to produce oppositely directed fluxes and being spaced apart a distance to produce a resulting selfinductance of substantial magnitude, the product of the number of turns and area of one coil section being related to the product of the number of turns and area of the other coil section so as to produce neutralizing magnetic fields at a distance, the said coil sections having windings of a size, number and arrangement to produce said resulting selfinductance of substantial magnitude combined with a small distributed capacity.

15. An astatic transformer comprising two windings, similar parts of the filaments of said windings being wound bifilarly, similar parts of the filaments of said windings being arranged in close juxtaposition throughout their lengths, said windings comprising a plurality of coil sections wound in opposite directions to produce oppositely directed fluxes and being spaced apart a distance to produce a resulting self-inductance of substantial magnitude, the said coil sections being spaced apart and the product of the number of turns and area of one coil section being related to the product of the number of turns and area of the other coil section so as to produce neutralizing magnetic fields at a distance.

Signed at New York, in the county of New York and State of New York, this 28th day of May, A. D. 1927.

LESTER L. JONES. 

